Over the last years, it has became more and more evident that artificial night lighting can have negative consequences for animals, especially for those who are active between dusk and dawn. Of course, different species react differently to different spectra of light; the dependence of these reactions on the spectral light distribution is, however, unknown for the vast majority of animal species, but it is possible to discern certain groups or trends. Many species are disturbed more by short wavelength light. This can have effects on the biological clock of both animals and humans, can influence the adaptation of the eyes to light or dark, or can influence behavior. Insects, for instance, are known to be more attracted by short wavelength light than by light of longer wavelengths. Bats show a lower avoidance of long wavelength light and rodents seem to perceive long wavelength light as darkness.
Another, well known example are sea turtles, where the females will not release their eggs on beaches with a lot of short wavelength light and where the young turtles emerging from the eggs are attracted to short wavelength light from inland instead of crawling towards the sea. The negative effects of lighting near ocean beaches on sea turtles have prompted cities to create ordinances which limit or restrict lighting near ocean beaches. These ordinances may require that light fixtures be turned off in some circumstances. Indeed, in or near protected habitats, all kinds of possible disturbances to animals should be kept to a minimum. But when the possible effects of accidents, involving human lives and direct effects on the environment as in traffic accidents or industrial calamities leading to chemical spills, fires, etc., outweigh the possible environmental effects, necessary precautions should be taken. One of the possible precautions is to have sufficient lighting for work and transport safety.
In an attempt to meet both the demand of lighting being not or hardly disturbing to animals and the demand of safety to humans, WO2005/107336 discloses a luminaire with two light sources. The luminaire is capable of selectively operating either a more or less monochromatic light source, not being disruptive to sea turtles and emitting in a wavelength range between 590 and 650 nm (for example a neon lamp radiating at wavelengths starting at around 585 nm), or an incandescent/fluorescent light source emitting light that is disruptive to sea turtles but pleasant and providing safety to humans. It is a disadvantage of the known light source/luminaire that it is rather expensive and relatively complex of construction. Another disadvantage of the known light source/luminaire is that it produces unpleasant light which only contributes to a relatively low extent to the safety of humans when the luminaire operates said monochromatic light source.